* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Figure 9-1 - Center for Invertebrate Biology
Selfish brain theory wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Neuroplasticity wikipedia , lookup
Optogenetics wikipedia , lookup
Brain morphometry wikipedia , lookup
Cognitive neuroscience wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Nervous system network models wikipedia , lookup
Subventricular zone wikipedia , lookup
Neuropsychology wikipedia , lookup
History of neuroimaging wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Blood–brain barrier wikipedia , lookup
Neural engineering wikipedia , lookup
Metastability in the brain wikipedia , lookup
Circumventricular organs wikipedia , lookup
Haemodynamic response wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Chapter 9 Part 1 Central Nervous System Exam 1 has been graded Class average = 79% Figure 9-1 Evolution of the nervous system: same basic principles action potentials, neurotransmitters at synapses, etc.) apply to all nervous systems Copyright © 2010 Pearson Education, Inc. CNS Development Early embryo, nervous system cells lie in a flattened area called the neural plate Day 20: Neural Plate cells along the edge migrate toward midline (Fig. 9-2a, p. 299) Neural Plate cells are purple in the figure Neural Crest cells are red Day 23: Neural Plate cells fuse, creating the Neural Tube (Fig. 9-2b, p. 299) Figure 9-2a Copyright © 2010 Pearson Education, Inc. Figure 9-2b Copyright © 2010 Pearson Education, Inc. CNS Development Neural Tube then develops into the entire CNS Lumen of neural tube remains hollow, becomes the central cavity of the CNS Cells forming the lining of the tube will differentiate into ependymal cells or remain as neural stem cells Outer cell layers of the tube become the neurons and glia Neural crest cells become the sensory and motor neurons of the PNS Figure 9-3a At 4 weeks, anterior end of tube has specialized into 3 brain regions: Forebrain Midbrain Hindbrain Copyright © 2010 Pearson Education, Inc. Figure 9-3b Brain at 6 weeks Central cavity becomes the ventricles Copyright © 2010 Pearson Education, Inc. Figure 9-3c Brain at 11 weeks Cerebrum expanding rapidly Copyright © 2010 Pearson Education, Inc. Figure 9-3d At birth, cerebrum developing furrows and ridges Copyright © 2010 Pearson Education, Inc. Figure 9-3e Due to flexion in neural tube during development, “dorsal and ventral” are different Copyright © 2010 Pearson Education, Inc. CNS Structure Composed of neurons and glial cells Interneurons are only found in the CNS Afferent and Efferent neurons link interneurons to peripheral receptors and effectors CNS divided into gray matter and white matter (Fig. 9-4c, p. 302) Figure 9-4, part 2 Copyright © 2010 Pearson Education, Inc. CNS Structure Gray matter: unmyelinated nerve cell bodies, dendrites and axon terminals Cell bodies are organized into either layers or clusters, depending on where they are in the CNS Clusters are known as nuclei in the brain and spinal cord Nuclei often have names: Lateral geniculate nucleus: processes visual information CNS Structure White matter: mostly myelinated axons; also has a few cell bodies It is white because of the myelin Tracts: bundles of axons in the CNS Tracts are the equivalent of nerves (PNS) Bone and connective tissue in the CNS Bone provides support and protection Brain is encased in the skull or cranium Spinal cord runs through a canal in the vertebral column Each vertebra is separated by disks of connective tissue PNS nerves enter and leave the spinal cord through notches between the vertebrae (Figure 9-4c) Figure 9-4, part 2 Copyright © 2010 Pearson Education, Inc. Meninges 3 layers covers brain and spinal cord offers additional protection Outermost layer: Dura Mater Very thick, durable Middle layer: Arachnoid membrane Looks like a spiderweb, loosely tied to pia mater The space in between the 2 layers is the subarachnoid space Meninges Innermost layer: Pia Mater Very thin and delicate, carries arteries which supply the brain Figure 9-4, part 1 Copyright © 2010 Pearson Education, Inc. Figure 9-4, overview Copyright © 2010 Pearson Education, Inc. Extracellular fluid in CNS (p. 301) Cerebrospinal fluid – Found in the brain ventricles and in the subarachnoid space Interstitial fluid – Interstitial: “in between” – In CNS, interstitial fluid is located inside the pia mater Figure 9-5a Copyright © 2010 Pearson Education, Inc. Cerebrospinal fluid (CSF) Secreted by the Choroid Plexus (fig. 9-5, p. 304) • Cells are similar to kidney cells • They selectively pump Na+ and other solutes from the blood plasma into the ventricles • This sets up an osmotic gradient which allows water to flow into the ventricles Figure 9-5bc Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid Circulation CSF is made in the choroid plexus, inside the third ventricle From the ventricles, the CSF flows into the subarachnoid space Then, within the subarachnoid space, it circulates around the CNS CSF is reabsorbed by Arachnoid Villi in the cranium (fig. 9-5d, p. 304) Figure 9-5bd Copyright © 2010 Pearson Education, Inc. Figure 9-5d Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid Functions Brain and spinal cord “float” in the CSF • CSF buoyancy reduces the weight of the brain nearly thirty-fold, decreasing pressure on blood vessels and attached nerves • CSF provides additional padding in case of blows to the head, etc. CSF provides a closely regulated chemical environment for CNS cells Cerebrospinal Fluid Functions Compared to blood plasma, CSF has different concentrations of ions: • Na+ conc is same as plasma • CSF has higher conc of H+ ions • CSF has lower conc of K+, Ca++, HCO3-, glucose HCO3- is the carbonate ion Cerebrospinal Fluid – CSF normally contains little protein and no blood cells Spinal tap or lumbar puncture – Withdraw fluid from the subarachnoid space of the lower vertebrae – If proteins and or blood cells are present in the CSF sample, then an infection may be present Blood-Brain Barrier Figure 9-6, p. 303-304 Brain capillaries are very highly selectively permeable. They only allow certain substances to cross over into the brain The endothelial cells of the capillary form tight junctions with one another This keeps out toxins and other harmful substances Blood-Brain Barrier Figure 9-6, p. 303-304 Tight junction formation in the endothelial cells is promoted by release of paracrines from the foot processes of the astrocytes. The foot-processes sit right on top of the brain capillaries (fig. 9-6) Figure 9-6 Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier Blood-brain barrier excludes water-soluble substances, but some lipid-soluble substances can diffuse across – This is why some antihistamines make you sleepy (they can diffuse across into the brain) while others don't – Most substances require carrier proteins to cross the blood-brain barrier (see p. 303 for details) Blood-Brain Barrier makes it difficult to treat many diseases—often won't let the intended treatment cross over into the brain Example: Parkinson's disease Dopamine (neurotransmitter) levels are too low due to damaged/dead dopaminergic neurons Can be treated by adding L-dopa, a precursor to dopamine Dopamine, administered as a pill or an injection, would theoretically treat the problem, but dopamine can't cross the barrier L-dopa, a precursor to dopamine, can cross the bloodbrain barrier Once in the brain, L-dopa is metabolized to dopamine Several brain areas lack the blood-brain barrier since these areas need to be in direct contact with the rest of the body: Hypothalamus – Releases neurosecretory hormones into the capillaries which then circulate over to the anterior pituitary Vomit center in the medulla oblongata – Tests blood for toxins, induces vomiting if toxins are found Brain cells require constant supply of both glucose and oxygen: Glucose • Requires transport proteins to move across into the brain • Only source of energy for neurons • Brain uses one half of body's glucose consumption • During starvation, brain can metabolize ketones produced by breaking down fat Oxygen • Freely diffuses across the barrier • Brain receives 15% of the blood pumped by the heart Brain damage can occur after only a few minutes if the brain is deprived of either oxygen or glucose – – Progressive hypoglycemia (low blood sugar) can lead to confusion, unconsciousness, and death Spinal Cord Divided into 4 regions (same as vertebrae) – Cervical – Thoracic – Lumbar – Sacral Regions are subdivided into segments Each segment gives rise to a bilateral pair of spinal nerves Figure 9-7 Copyright © 2010 Pearson Education, Inc. Spinal Cord Spinal Nerves – Just before joining the spinal cord, each nerve divides into two branches or roots – Dorsal root carries incoming sensory information – Dorsal root ganglion has the cell bodies of the sensory nerves – Ventral root carries information from the CNS out to the muscles and glands Figure 9-7 Copyright © 2010 Pearson Education, Inc. Gray matter: – The butterfly or H-shaped center – Dorsal horns: sensory fibers synapse with interneurons here – Ventral horns: cell bodies of motor neurons which carry White matter: – The white area around the central butterfly • Contains tracts (ascending, descending, propriospinal) Spinal Reflexes Spinal cord can function as a self-contained integrating center for simple spinal reflexes Figure 9-7 Copyright © 2010 Pearson Education, Inc. Figure 9-8 Copyright © 2010 Pearson Education, Inc. Figure 9-9, overview Copyright © 2010 Pearson Education, Inc. Figure 9-9-1 Copyright © 2010 Pearson Education, Inc. Table 9-1 Copyright © 2010 Pearson Education, Inc. Figure 9-10 Copyright © 2010 Pearson Education, Inc. Figure 9-13 Copyright © 2010 Pearson Education, Inc. Figure 9-14 Copyright © 2010 Pearson Education, Inc. Figure 9-15 Copyright © 2010 Pearson Education, Inc. Figure 9-16 Copyright © 2010 Pearson Education, Inc. Figure 9-17 Copyright © 2010 Pearson Education, Inc. Figure 9-18 Copyright © 2010 Pearson Education, Inc. Figure 9-11 Copyright © 2010 Pearson Education, Inc. Figure 9-12 Copyright © 2010 Pearson Education, Inc.